Observation of the rare baryonic decay $B^{+}\to p\bar{\Lambda }$ and measurement of its weak decay parameter

Abstract

The first observation of the decay $B^{+}\to p\bar{\Lambda }$ is presented, using proton-proton collision data collected by the LHCb experiment between 2016 and 2018 at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$. The signal significance exceeds seven standard deviations. Using the $B^{+}\to K_{\mathrm{S}}^0{\pi }^{+}$ decay as a normalization channel, the branching fraction is measured and combined with previous LHCb results based on data collected at 7 and 8 TeV in 2011 and 2012, yielding $\mathcal{B}(B^{+}\to p\bar{\Lambda })=(1.24\pm 0.17\pm 0.05\pm 0.03)\times 10^{-7}$, where the first uncertainty is statistical, the second is systematic, and the third comes from the uncertainty on the branching fraction of the normalization channel. The $B^{+}\to p\bar{\Lambda }$ weak decay parameter is measured to be ${\alpha }_B=0.87_{-0.29}^{+0.26}\pm 0.09$, indicating the presence of comparable S-wave and P-wave decay amplitudes.

arXiv commentAll figures and tables, along with any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/5350/ (LHCb public pages)

References in corpus (38)

• PYTHIA 6.4 Physics and Manual
• PYTHIA 6.2 Physics and Manual
• A Brief Introduction to PYTHIA 8.1
• LHCb Detector Performance
• PHOTOS Monte Carlo: a precision tool for QED corrections in Z and W decays
• sPlot: a statistical tool to unfold data distributions
• The LHCb Trigger and its Performance in 2011
• Kernel Estimation in High-Energy Physics
• Mass distributions marginalized over per-event errors
• Selection and processing of calibration samples to measure the particle identification performance of the LHCb experiment in Run 2
• Design and performance of the LHCb trigger and full real-time reconstruction in Run 2 of the LHC
• Precise Measurements of Decay Parameters and $CP$ Asymmetry with Entangled $\Lambda -\bar{\Lambda }$ Pairs
• Measurement of CP Asymmetries and Branching Fractions in Charmless Two-Body B-Meson Decays to Pions and Kaons
• Charmless Exclusive Baryonic B Decays
• Observation of CP Violation in B0 -> K+pi- and B0 -> pi+pi-
• Study of B0 -> pi0 pi0, B -> pi pi0, and B -> K pi0 Decays, and Isospin Analysis of B -> pipi Decays
• Observation of Direct CP-Violation in B0 --> pi+pi- Decays and Model-Independent Constraints on phi2
• Measurement of $CP$ asymmetries in two-body $B_{(s)}^0$-meson decays to charged pions and kaons
• Observation of the annihilation decay mode $B^0\to K^{+}{K}^{-}$
• Observation of B Decays to Two Kaons
• Violation of PCAC and two-body baryonic $B$ and $D_s$ decays
• Measurement of CP asymmetries in $B^0\to K^0{\pi }^0$ decays
• Improved measurements of branching fractions for B -> K pi and B -> pi pi decays
• Observation of $CP$ violation in two-body $B_{(\mathrm{s})}^0$-meson decays to charged pions and kaons
• Search for Exclusive Rare Baryonic Decays of $B$ Mesons
• Charmless Two-body Baryonic $B_{u,d,s}$ Decays Revisited
• Measurement of CP violation in the decay $B^{+}\to K^{+}{\pi }^0$
• Studies of the decays $B^{+}\to p\bar{p}{h}^{+}$ and observation of $B^{+}\to \bar{\Lambda }(1520)p$
• First observation of the rare purely baryonic decay $B^0\to p\bar{p}$
• Measurement of the CP-Violating Asymmetries in B0 -> KS pi0 and of the Branching Fraction of B0 -> K0 pi0
• Rates and $CP$ asymmetries of Charmless Two-body Baryonic $B_{u,d,s}$ Decays
• On the smallness of Tree-dominated Charmless Two-body Baryonic $B$ Decay Rates
• Evidence for the two-body charmless baryonic decay $B^{+}\to p\bar{\Lambda }$
• Observation of the $B_s^0\to {\eta }^{\prime }{\eta }^{\prime }$ decay
• Baryonic $B$ meson decays
• Measurement of $CP$ asymmetries in ${\Lambda }_b^0\to p{h}^{-}$ decays
• Measurement of the branching fraction of the decay $B_s^0\to K_S^0{K}_S^0$
• Search for the rare hadronic decay $B_s^0\to p\bar{p}$